Punch press with die holder adjusting and locking means



Feb. 20, 1962 P. s. JACKSON 3,021,742

PUNCH PRESS WITH DIE HOLDER ADJUSTING AND LOCKING MEANS Original Filed Feb. 7, 1952 5 Sheets-Sheet 1 i E3? INVENTOR.

6f Jae/c602, l & M, W

Feb. 20, 1962 P. s. JACKSON 3,021,742

PUNCH PRESS WITH DIE HOLDER ADJUSTING AND LOCKING MEANS 5 Sheets-Sheet 2 Original Filed Feb. 7, 1952 INVENTOR. laal. Jackson, BY /M W Feb. 20, 1962 P. s. JACKSON PUNCH PRESS WITH DIE HOLDER ADJUSTING AND LOCKING MEANS 5 Sheets-Sheet 5 Original Filed Feb. 7, 1952 mmvron. Paul 5 Jae/6027 Feb. 20,1962 P. s. JACKSON 3,021,742

PUNCH PRESS WITH DIE HOLDER ADJUSTING AND LOCKING MEANS Original Filed Feb. 7, 1952 5 Sheets-Sheet 5 tare are This invention relates to a press, and particularly to a punch press including meansfor adjusting-the die of the press toward and away from the ram.

It is the general object of this invention to produce new and improved apparatus as described in the preceding paragraph.

This application is a division of my pending application Serial Number 270,377, filed February 7, 1952 now Patent No. 2,808,736.

It is usually required in a punch press to provide some means for adjusting the position of the punches in the ram relative to the die mounted on the bolster or press or press frame below. This adjustment normally requires the use of one or more heavy adjusting screws and a locking device mounted on the ram. Inasmuch as the punch press disclosed herein is designed for heavy duty, high speed operation, it is desirable to reduce the weight of the ram as much as possible so as to reduce the over-all required weight of the press including the counterbalance system. As an additional feature of the invention, I provide a movable die holder on the frame of the press which is adapted to be moved by the adjusting screws and to be held in adjusted position by locking devices. Thus, the necessary adjustment of the relationship between the ram and the die is achieved not by means mounted on the ram, as has heretofore been the practice, but rather by means mounted on the frame apart from the ram.

Another feature of the invention is the provision in a die adjusting mechanism of the type mentioned in the preceding paragraph of a plurality of adjusting screws which may be motor driven so as rapidly to elfect the raising and lowering of the die relative to the ram together with an easily operated locking mechanism which serves to lock the screws in adjusted position.

Other and further features and objects of the invention will be readily apparent from the following description and drawings, in which:

FIG. 1 is a top plan view of a punch press embodying the feature of the invention;

FIG. 2 is a side elevation of the upper portion of the press, partially broken away for clarity of illustration, taken on line 2-2 of FIG. 1;

FIG. 3 is a front elevational view of the lower portion of the press showing a part of the feed mechanism and the means for adjusting the die;

FIG. 4 is a vertical sectional view of the press taken along line 44 of FIGS. 2 and 3; and

FIG. 5 is a horizontal sectional view through the upper portion of the press taken along line 55 of FIG. 2.

While this invention is susceptible of embodiments in many dilferent forms, there is shown in the drawings and will herein be described in detail one specific embodiment, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

Referring now to FIG. 4, the apparatus of this invention is shown as incorporated in a punchpress including a frame A which supports at its top a driving mechanism B for driving the crankshaft system C of the press. The crankshaft system is connected to a ram D for reciprocating the same toward and away from the die E of the press, with the die being supported on an adjusting system F.

The frame includes a pair of vertical steel panels or side plates 10 and 11 which carries the mechanism of the press and which are provided with aligned openings 12 and 13 through which a workpiece is passed through and beneath the ram of the press. Supported at the top of the side plates is a pair of spaced horizontal top plates 1414a which carry an electric motor 15 for driving the press through the medium of a pulley 16 secured to the drive shaft of the motor which carries a plurality of V-belts 17 engaging a second pulley 18 secured to one of the drive shafts 19 of the press. As best shown in FIG. 1, the top of the ram carries a plurality of oil lines 20 which serve to lubricate various portions of the press, as will hereinafter be described. cover 14b is secured to the top plates and extends over the space therebetween to prevent oil from splashing upwardly as the ram is reciprocated.

Referring now to FIG. 5, parallel to and horizontally spaced from the crankshaft 19 is a second crankshaft 21, with both crankshafts being rotatably mounted on relatively massive, anti-friction bearings 22 carried by the side plates of the frame. Each of the bearings is mounted on a conical-shaped removable sleeve 23 machined properly to fit the outer surface of the crankshaft and the inside of the inner bearing race of each of the bearings 22. Fixed to the crankshaft 19 adjacent the ends thereof is a pair of gears 24 and 25 which mesh with a similar pair of gears 26 and 27 secured to the crankshaft 21 The gears are in a 1 to 1 ratio so that rotation of the shaft 19 in one direction through the medium of the driving pulley 18 rotates the shaft 21 at the same speed but in the opposite direction. The gears are each mounted on removal sleeves 28 and spaced from the bearings 22 by spacers 30a. The removal sleeves 28 are held in position by nuts 29 which, after being tightened in position are held against slippage by keyed lockwashers 30.

Integrally formed on each of the crankshafts 19 and 21 is a tapered eccentric 31 and 32. The eccentrics are oppositely positioned so as both to be facing toward the center line of the press in one position and horizontally outward from the center line when rotated with eccentrics being in aligned relationship in vertical planes so as to achieve the reciprocation of the ram.

As previously noted, the eccentrics 31 and 32 are tapered toward each end with the oppositely facing tapers on each eccentric being separated by integral rings 33 and '34 which act as spacers for pairs of anti-friction bearings 35 and 35a and 36 and 35a carried by the eccentrics 31 and 32 respectively. It will benoted that the inner surface of the bearing races of each of the anti-friction bearings in said pairs is tapered to facilitate press-fitting the pairs of bearings on the eccentrics. To provide for easy removal of the bearings when their replacement becomes necessary, each crankshaft is drilled as indicated at 37 to form an oil passage communicating with an annular oil groove 38- formed on each taper of each eccentric. Introduction of oil under pressure into the passages 37 and thence to the passages 38 spreads the inner side of the bearing races slightly but sufnciently to permit the hearings to be removed with ease.

Inasmuch as the drive shafts 19 and 21 are not symmetrical but rather are provided with off-center eccentrics, the drive shafts themselves would produce unbalance forces when rotated. To oif-set the unbalance of the crankshafts which is equal both at top and bottom e d e e tt of h aphid? is P v d i h A transparent plastic drilled openings 40 positioned on the same side of the crankshaft as the eccentricity of the eccentrics and serves to ofiset any unbalance produced by such eccentrics. The holes 49 may, if desired, be of a size suflicient only to counter-balance the eccentrics. If desired, theholes may be larger than necessary to counterbalance the eccentrics to further reduce the weight of the counterbalaincing mechanism for the entire press. For counterbalancing the ram which is reciprocated by the crankshafts, each of the gears 2427 is provided with counterbalance weights 41- 44 positioned oppositely from the holes 4% with the weights being removably held in a groove formed in the gear by the screw device illustrated. Counterbalance weight of different mass may be required depending upon the weight of the ram and punch assembly; and as punches are changed, which naturally results in a change in the weight of the ram, the counterbalance weights may also be changed. As previously mentioned, the weights maybe adjustably fixed on the gears, such as by mounting them .on-eccentric shafts, so that the weights may be moved inwardly toward or outwardly away from the axis of rotation of the crankshafts to increase or decrease the inertia of the weights and thus to adjust forvarying ram weights.

Aspreviously mentioned, slotted crossheads or scotc yokes are employedrfor translating the rotary movement of the eccentricsinto reciprocal movement of the ram. To this end each pair of bearings 35 and 35a and 36 and 36a is mounted in a crosshead slidable in suitable ways formed in a crosshead way frame. The crosshead way frame includes an upper plate in the form of a channel member 45 and a lower member 46. "The members are maintained in spaced parallel relationship by aluminum spacer blocks 47a, 47b and 47c. Bolts 48 pass through the members and blocks and are provided with suitable nuts 49 to maintain the frame in place. Upper and lower bronze bearing plates 50 and 51 are secured to the inner sides of the members 45 and 46 to provide slide bearings for a pair of crossheads "52 and 53 which in turn are carried by the bearings 35 and 35a, and 36 and 36a. Thus, movement of the eccentrics in a horizontalplane produces merely sliding movement between the crossheads and their ways while movement in vertical planes causes vertical movement of the crossheads and ways. The actual movement of the crossheads is circular but relative to the ways is a horizontal movement back and forth.

Secured to the center spacer block 47b is a pair of V- gibs 56 which extends vertically from top to bottom of the crosshead way frame and are slidable in suitably formed bearing surfaces 57 which are secured to the frame and extend vertically therealong. End gibs 58a and 58c are secured to the end spacer blacks 47a and 47a and are slidable on suitable bearing surfaces 59a and 59c also secured to the framework so as to provide a guided support means for the reciprocating parts of the press. The V construction of the center gibs makes an accurate center guide for the ram and still permits it to expand equally to both ends from the center.

Lubrication of the crossheads in their ways is supplied through the lubricating conduits previously noted. For the purpose of circulating the lubricating fluid, each of the spacer blocks 47a47c is provided with a lube oil passage 60a-6lc. Oil is introduced into suitable interconnected lubricating grooves formed in the bearing surfaces 50 and 51 through a lube oil connection 61 in turn connected to one of the oil lines 29. Lubricating oil in the grooves on the bearing surfaces passes outwardly from the connection of the line 61 thereto and circulates, by means of the spacer block passages Gila-60c, through simila lube oil grooves formed in the lower crosshead bearing surface. A suitable drainconnection is provided for the lower bearing surface 51 to produce a continuous circulation of lubricatingoil for thecrosshead way system.

The ram D comprises a welded steel arm 62 secured atits upper endtothe lower crosshead way frame member 46 and provided at its lower end with means for securing i thereto a punch holder 63, a punch liner 64 and upper and lower wedges 65. The punch holder, punch liner and upper and lower wedges are held in position on the arm 62 by clamps 66. A stripper plate 6'7 is carried by upper clamps 68 secured to side rails 69 fixed in the frame.

It will be noted that the ram assembly does not include the usual adjusting screws for adjusting the punches mounted on the punch holder relative to the die of the press. Thus, the weight of the ram is reduced to a minimum without in any manner detracting from, and in fact adding to, its strength. 7

The reciprocating ram of the press and its attendant accessories is substantially completely counterbalanced by the counterbalance-.veights attached to the gears hereinbefore described. It will be noted that the weigntsare located symmetrically about the center line of the reciprocating mass, that is are positioned equidistantly on both sides of such center line and symmetrically from and rear. Because of this symmetrical relationship of the counterbalance weight, no rocking couple is introduced'in the system and the weights, when acting in accumulative relationship, counterbalance the primary unbalance of the reciprocating ram and are in opposed relationship 90 from between top and bottom dead center of the ram (where the ram creates no primary unbalance) eiiectively to cancel out the transverse unbalance of the rotating weights. In the specific embodiment shown, the press is a one hundred ton punch press, the ram weighs about nine hundred pounds and the eccentrics have a quarter inch throw and thus impart a half inch stroke to the ram. Thus, the ram develops an inertia of two hundred twenty-five inch pounds. The counterbalance weights are about live and a-half inches from their axes of rotation and, as four are provided, each balances one fourth the mass-moment of the ram, thus each Weighs about ten pounds. With the press so counterbalanced, speeds up to live hundred strokes per minute have been achieved without creating vibrations sufiicient to tip a coin balanced on edgeon the press frame.

The .die assembly E comprises a die holder '79 having a suitable groove in which there is located a die shoe 71 which carries .a suitably formed die 72. Positioned on either side of the die are lower guides 73. The die holder '74 is clamped to a bottom plate 74 by a die clamp 75 and the bottom plate is bolted to a base plate or platen 76 movably mounted in the frame A. As previously noted, the die assembly E is provided with an adjusting means F for adjusting the die relative to the punches in the punch holder with the adjusting means being mounted on the frame rather than carried by the The adjusting means F are so designed as to facilitate vertical movement of the die on the frame properly to position it relative to the ram and also to permit rapid replacement of broken punches and the like. The adjusting means F is provided with a plurality-of screws 39 having external threads engaging the threads of an internally threaded collar 81 fixed to a lower cross brace 82 in the frame. A housing 83 is fixed to the lower side of the platen 76 and encloses a transversely extending drive shaft 84 carrying a plurality of worms 85 each engaging a worm gear 86 fixed to the lead screws 80. Thus, each of the screws 88 is provided with a worm gear 86 afiixed thereto-so that rotation of the screws and hence vertical movement of the platen may be achieved by rotating the shaft 84. If desired, a motor may be attached ,to the shaft 84, which motor may be operated by a suitable manual or pedal control to achieve rotation in either direction of the shaft 84 and hence to raise or lower the platen, and thus. the die, toward and away from the ram. It will be noted that the upper face of the worm gear 36 bears against a face portion 87 of the housing '83 and by movement thereagainst with rotation pf the screw accomplishes the vertical movement of the platen.

It is necessary after making an adjustment of the die relative to the ram, that is after rotating the adjusting screws 50, that the screws be locked in adjusted position to prevent creeping during the operation of the press. To this end one or more of the lead screws are hollow and provided with locking means to prevent such creeping movement. It the exemplary embodiment of the invention shown, three of the screws 84 are so constructed, thus as seen in FIG. 4, wherein one of such hollow screws is illustrated, there is provided a locking rod 90 secured by means of the key 91 in hollow 92 formed in the lead screw 31). The keyed connection between the screw and the locking rod is such as to prevent relative rotation between the screw and the rod but to permit sliding longitudinal movement between the rod and the screw. The lower end of the locking rod is threaded at 93 with the threads having the same pitch as the threads formed on the exterior surface of the lead screws 30 and with the threads 93 engaging threads formed in the interior of a worm gear 94-. A worm 95 fixed to a rotatable shaft 96 engages the teeth of the gear 94 so that rotation of the shaft 96 causes rotation of the worm gear 94. The upper end 97 of the rod is provided with a collar 93 to hold the rod in position with the lower face of the collar being adapted to bear against the upper portion of thebottom plate 74. A foot treadle 99 (FIG. 3) is provided for rotating the shaft 96 and hence to rotate all of the worm gears 94. Inasmuch as the threads formed at the lower end of the locking rod have the same pitch as the threads on the lead screw and as the key-way 91 causes the screw and rod to rotate together, vertical adjustment of the platen may be achieved through rotation of the shaft 84. The similar pitch of the threads in the rod and screw permits such rotational movement without corresponding rotation of the worm gear 9 When the platen has been moved to the desired position, it is merely necessary for the operator to step on the treadle 99 to cause rotation of the shaft 96 and hence of the worm gears 94-. Such movement serves to move the rod 90 downwardly to bring the lower face of the collar against the upper face of the bottom plate and thus to apply sufiicient tension on the lead screw and rod as to prevent their rotating with operation of the press. To release the adjusting means for further adjustment, it is merely necessary to rotate the shaft 96 in the opposite direction, thus releasing the locking means.

Means are provided on the press for feeding aworkpiece is predetermined increments to the ram and die during the reciprocation of the ram. For this purpose there is mounted on the platen 76 two pairs of feed rolls 13fi1%1 and Mina-1111:: with the rolls in each pair being vertically arranged and with the pairs being located on opposite sides of the dief The rolls are rotatably mounted on the platen, for example as shown in FIG. 3 the lower rolls 100-4631: and upper rolls 1011-1011: are suitably journaled in. bearings 10212a and "RH-103a at each end. Secured to the shaft carrying each of the rolls is an upper drive gear 194 and'a lower drive gear 1115. The rolls are pressed together by pneumatic piston and cylinder devices 1% mounted at each end of the upper roll and. means are provided for operating such devices to separate the rolls slightly to permit insertion of a workpiece in the nip between the rolls. The teeth on the gears 134 and 195 are made extra long so that they remain inlmesh in all positions of the upper roll relative to the lower roll. If desired, a lubricant may be supplied to the workpiece by the upper roll 1111 and to this end it may he provided with a hollow shaft connected to a suitable lube line 108 which feeds lubricant into the interior of the upper roll from which it is extruded through small openings 109 in the surface of the'roll and onto the surface of the workpiec The lower roll rotates in a pan 11! of lubricant to supply its surface with oil.

A friction clutch, such as the clut eh 111, is provided for the lower roll of each pair and is so designed as to prevent rotation of the rolls except through the positive action of feed means hereinafter to be described. Thus, when the rolls are stationary, the workpiece held therein is maintained in fixed relationship relative to the ram and die and backlash or slippage of the rolls and hence of the workpiece is prevented.

The feed rollers and 101 are located at the entering side of the workpiece while the opposite pair of feed rolls 100a and 101a is at the exit side. The upper roll 161a of the exit feed rolls may also be provided with pneumatic devices 112 for raising and lowering the upper roll relative to the lower roll 100a for the purpose of permitting the initial insertion of a workpiece.

Means are provided for rotating both pairs of feed rolls in unison and by predetermined increments to feed a workpiece through the press. To provide for such intermittent movement of the feed .rolls there is provided a rod (FIG. 2) threaded intothe crosshead 52' and pivotally connected to a second rod 121 in turn connected by a link 1212 to a shaft 123 rotatably mounted in the frame. The shaft carries a block 124 provided with a dovetailed groove 125 in which'is slidably' mounted a block 126 rotatably carrying an actuating rod 127. With operation of the press the rotary movement (relative to the fixed frame) of the crosshead 52 is imparted to the rod 120 and translated by the link 122 into oscillatory movement of the shaft 123 and hence pivotal rocking movement of the block 124. The slide block 126 may be secured in the groove 125 at any desired position away from the axis of rotation of the block so as to impart to the actuating rod 127 whatever degree of vertical reciprocation is desired, ranging from zero, when its pivotal connection to the slide block coincides with the axis of movemnet of the block 24, to maximum, when the block is adjacent the end of the dovetailed groove.

The actuating rod 127 is connected at its lower end to a vertically reciprocable member 128 having rack teeth thereon engaging teeth 129 on a gear 130 fixed to a clutch shaft 131 having one end journaled in a pillow block 132 fixed to the platen, and having its other end supported in a free-wheeling indexing type clutch 133. The clutch 133 is of well known construction adapted to impart to the drive gear 105 motion in one direction only in response to the oscillatory movement of the shaft 131.

The gears 104 and 105 are connected through a gear train (not shown) to similar gears connected to the top and bottom rollers of the other pair of feed rollers so that both pairs of feed rollers are simultaneously driven. The gear corresponding to the gear 105 secured to the roll 100a is connected through a second free-wheeling indexing type clutch, clutch shaft, gear and rack to the piston of an air cylinder 134 which is adapted, when air under pressure is introduced into the cylinder, to rotate both pairs of feed rollers rapidly to advance a workpiece through the press.

The gear 130 may be shifted along the shaft 131 to disengage its teeth from those of the rack 129. To this end there is provided a hand lever 135 pivoted at 136 to the frame and secured to a pair of vertically spaced arms 137 and 1371; each carrying detents 138 and 138a which ride in an annular groove 139 formed in the gear 130. Movement of the handle 135 slides the gear teeth out of mesh with the rack teeth to disconnect the feed mechanism.

If a series of perforations are to be made in a workpiece, for example the perforations in the back panel of a radio or televeision set, a long workpiece may be inserted in the rolls and the press started. Each stroke of the ram punches one row of holes in the workpiece and on each stroke the feed mechanism serves to rotate both pairs of feed I rolls and advance the workpiece slightly to determinethe spacing between perforations. When the, required number of rows of perforations has been punched in the workpiece,'the air cylinder 134is operated, either manually or by suitable automatic controls, rapidly to rotate both pairs of feed rollers a distance greater than their rotation during the feed operation and thus to provide a space between the first series of perforations and a succeeding series. Both feed and rapid speed mechanisms operate while the punches are out of contact with the workpiece, that is they operate when the ram is moving upwardly toward top deadcenter and during only a portion of the rams movement downwardly toward the die and workpiece. To prevent operation of the air cylinder when the punches are in contact with the workpiece, a suitable limit switch may be incor porated in the electrical engergizing means for the air cylinder valve to permit such energization only when the ram is near top dead center.

It will be noted that the feed rolls and. most of the feed mechanism is carried by the platen and thus adjustments of the platen upwardly or downwardly do not misalign' the feed rolls. If desired, the feed rolls may be provided with an individual adjustment to lower the position of the lower rolls as the dies are reground, thus making it a simple matter to keep the top of the lower roll of each pair in the same plane as the reground die. A similar adjustment'is not necessary for the upper rolls inasmuch as the air cylinders with which each of the upper rolls is provided serves to move those rolls downwardly against its associated lower roll.

The die holder 76 is provided with openings at the location of the die so that the small portions of the workpiece which are punched out by the punches drop therethrough onto a waste conveyor belt 149 suitably mounted on rollers 141, one of which 141a is driven by a motor 142. The belt is driven in the direction indicated by the arrow so that the waste slugs are carried on the upper surface of the belt toward a chute 143 positioned at the left-hand side of the press (as seen in FIG. 3) and as the belt passes aroundthe first roller 141, such slugs drop ofi into the waste chute.

I claim: 7

1. Means for adjusting the position of the die of a punch press having a ram and a frame comprising, a base plate, means on the base plate for securing the die thereto, a plurality of screw devices threadedly engaging the frame and carrying the base plate, means for rotating said screw devices simultaneously to raise and lower the base plate toward and away from the ram of the press, and means, including an elongated rod having a shoulder engaging the top of said base plate, slidably connected to said base plate and to at least one of said screw devices for axially stressing the threads of said screw devices against the threaded portion of said frame and locking said base plate in adjusted position.

2. Means for adjusting the position of the die of a punch press having a ram and a frame comprising, a plurality of vertically arranged screw devices threadedly engaging the frame, at least one of said screw devices being hollow, a base plate carried by the screw devices, means on the base plate for securing the die thereto, worm gears secured to each screw device and rotatable relative to the base plate, a power shaft rotatably mounted on and extending along the base plate adjacent each of the gears, a plurality of worms secured in spaced relationship on the shaft each engaging a different one of said gears whereby rotation of the shaft causes simultaneous rotation of the screw devices to raise or lower the base plate toward and away from the ram of the press, and means ineluding an elongated rod having a shoulder engaging the top'of said base plate sl-idably mounted in said base plate and in at least one of said hollows for axially stressing the threads of said screws against the threaded portion of said frame and securing the base plate in adjusted position.

3. Means for adjusting the position of the die of a P c p es ha ng a ra and a f m c mp s a plurality ofv'ertically' arranged screw device's threadedly engaging the frame with at least one of said screw devices being hollow, a base plate having at least one bore therein carried by the screw devices, means on the base plate for securing the die thereto, worm gears secured to each screw device, a power shaft rotatably mounted on and extending along the base plate adjacent each of the gears, a plurality of worms secured in spaced relationship on the shaft, each engaging a different one of said gears, whereby rotation of the shaft causes simultaneous rotation of the screw devices to raise or lower the base plate toward and away from the ram of the press, an elongated locking rod having an exteriorly bottom end and a top end provided with a shoulder extending through said bore and said hollow, means securing the rod to the screw device in a manner permitting longitudinal movement and preventing relative rotational movement therebetween, a locking nut engaging the threads on the bottom portion of said rod and rotatably mounted in the frame, and means for rotating the nut to move the rod longitudinally downward relative to said screw device and base plate bringing the under surface of said shoulder against the upper surface of said base plate to frictionally lock the screw device in adjusted position.

4. Means for adjusting the position of the die of a punch press having a ram and a frame comprising, a plurality of vertically arranged screw devices threadedly engaging the frame with at least some of said screw devices being hollow, a base plate having at least some bores therein carried by the screw devices, said bores being directly above said hollows, means on the base plate for securing the die thereto, worm gears secured to each screw device, a power shaft rotatably mounted in and extending along the base plate adjacent each of the gears, a plurality of worms secured in spaced relationship on the shaft, each engaging a different one of said gears whereby rotation of the shaft causes simultaneous rotation of the screw devices to raise or lower the base plate toward and away from the ram of a press, an elongated locking rod having exteriorly threaded bottom end and a top end provided with a shoulder extending through each of said bores and said hollows with each rod being keyed to its associated screw device in a manner permitting relative longitudinal movement and preventing relative rotational movement therebetween, locking nuts rotatably mounted in the frame and each engaging the threads on the bottom portions of said rods, said threads having the same pitch as the pitch of the threads of the screw devices, a locking shaft rotatably mounted in the frame and extending adjacentsaid locking nuts, a plurality of worms secured to the locking shaft, each engaging worm gear teeth formed on the exterior surface of said locking nuts, and means for rotating the locking shaft to rotate said nuts thereby causing the rods to move downwardly within the hollows and bring the uudersurface of said shoulder against the top surface of said base plate to frictionally lock all of the screw devices in adjusted position.

References Cited in the file of this patent UNITED STATES PATENTS 457,132 Rheutan Aug. 4, 1891 921,503 Bates May 11, 1909 1,166,049 Hyde Dec. 28, 1915 2,053,313 Ballard Sept. 8, 1936 2,285,717 Indge June 9, 1942 2,318,107 Scheifey May 4, 1943 2,337,984 Flowers Dec. 28, 1943 2,451,636 Spiller Oct. 19, 1948 2,467,546 Anderson Apr. 19, 1949 2,696,251 Hawkes Dec. 7, 1954 2,751,984 Kuhl June 26, 1956 2,808,736 Jackson Oct. 8, 1957 FOREIGN PATENTS 528,497 Great Britain Oct; 30, 1940 

